Composite structural part comprising pyrotechnic detonating rupture means

ABSTRACT

A pyrotechnically-ruptureable composite structural component, intended to transmit forces between first and second structural elements, has an elongate pyrotechnic detonation separation component incorporated in the structural component for breaking the structural component and separating the first and second elements. The structural component has a first part in which the pyrotechnic separation component is incorporated and which is able to be connected to the first element, and a second part that connects to the second element. The first and second parts are rigidly assembled via their free ends, which are the opposite ends to the first and second elements respectively. The rigid assembly has a damper arranged between the free ends of the first and second elements so as to damp a detonation shock propagating to the free end of the first part when the pyrotechnic separation component is detonated.

FIELD OF THE INVENTION

The present invention relates to a pyrotechnic detonating ruptureablecomposite structural component quite particularly, although notexclusively, suited for use in space launchers. It will be describedhereinafter more particularly in the latter application.

BACKGROUND OF THE RELATED ART

It is known that certain elements of space launchers, such as adjacentstages, are mechanically joined together by a composite structuralcomponent intended to transmit mechanical forces between said elementsas necessary and provided with pyrotechnic detonation separation meansincorporated in said structural component and able to break it along thestraight or curved line of separation when said elements have to beseparated from one another. Similar composite structural components alsoallow the satellite bearing structures to be severed on board launchers.

At the moment of rupture of such a structural component, that is to sayat the moment of separation of the structural elements it secures, saidpyrotechnic separation means generate a detonation shock of highamplitude, high frequency, and with a high propagation speed (severalkilometers per second), propagating through the structure to which saidelements belong, the amplitude and the frequency of said shockdiminishing as it propagates through the structure.

Hence, in order to protect the equipment and the payload which arecontained in said structural elements, it is common practice to providea plurality of discrete damping means, generally sheets or strips ofvisco-elastic material, near said equipment and near the payload, so asto attenuate the shock, the amplitude and frequency of which havealready been diminished by the propagation.

It will be noted that the arrangement of such a plurality of discreteattenuation means increases the complexity and the time taken to mountsaid equipment and the payload in the launcher.

SUMMARY OF THE INVENTION

It is the main object of the present invention to remedy thisdisadvantage.

To this end, according to the invention, the pyrotechnically ruptureablecomposite structural component:

-   -   intended to transmit forces between a first and a second        structural element; and    -   provided with elongate pyrotechnic detonation separation means        incorporated in said structural component and able to break it        so that said first element can be separated from said second        element along a line of separation,        is notable:    -   in that it comprises:        -   a first part in which said pyrotechnic separation means are            incorporated and which is able to be connected to said first            element;        -   a second part able to be connected to said second element;            and        -   means of rigid assembly of said first and second parts via            their free ends which are the opposite ends to said first            and second elements respectively; and    -   in that said assembly means comprise damping means:        -   arranged between the free ends of said first and second            elements; and        -   able to damp the detonation shock propagating to the free            end of said first part when said pyrotechnic separation            means are detonated.

Thus, according to the invention, said damping means are incorporatedinto said composite structural component, just as are said pyrotechnicseparation means. As a result, the detonating shock is damped at sourceand there is no longer any need to position a plurality of dampers nearthe equipment and near the payload. In addition, the effectiveness ofthe damping means is high because the amplitude of the shock has not yetbeen diminished when the shock reaches said damping means.

It will also be noted that, from an industrial standpoint, the presentinvention is advantageous because it makes it possible to obtain asingle composite component incorporating the pyrotechnic separationmeans and the means of damping the detonation shock.

As a preference, said assembly means form a chamber enclosing said freeends of said first and second parts and confining said damping meansbetween said free ends. Such a chamber may be formed by lateral platesarranged on each side of said free ends and secured only to said secondpart.

Thus, said damping means not only damp the detonation shock but alsostiffen the means of assembly between said first and second parts ofsaid composite structural component. They therefore simultaneously forma barrier to the detonation waves and a mechanical connection betweensaid first and second parts.

To this end, it is advantageous for said damping means to extendlaterally between said lateral plates and said free end of said firstpart and to be confined there and for the free end of said first part tocomprise a widened head.

Thus, said damping means may have a cross section in at least theapproximate shape of a stylized omega, the internal cavity of which isfilled by said widened head. The result of this shape is that,regardless of the direction and nature of the forces applied to saidassembly means, these means cause at least part of said damping means tobe compressed. The stiffness of said assembly means therefore dependsprimarily on the compressibility of the material of which said dampingmeans are made. Such a material may be of the visco-elastic type and bechosen, for example, from among natural rubbers, silicones,acrylonitrile butadienes or polyurethanes.

For reasons of convenience, it is preferable for said damping means tobe in the form of an open section placed over the free end of said firstpart to enclose it.

It is advantageous for the surface of said damping means in contact withthe free end of said first part to comprise cavities allowing thematerial of said damping means to expand even when these means aresubjected to weak mechanical stresses. In the case of strong stresses,as the cavities are immediately filled by said damping means, thematerial of these means is made to work in volumetric compressibility.Said cavities are therefore able, to a certain extent, to adapt thestiffness of said damping means according to the level of mechanicalstress.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures of the attached drawing will make it easy to understand howthe invention may be embodied. In these figures, identical referencesdenote similar elements.

FIG. 1 illustrates, in cross section, one exemplary embodiment of thepyrotechnically ruptureable composite structural component according tothe present invention.

FIG. 2 is an exploded perspective view showing certain constituent partsof the structural component depicted by way of example in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The pyrotechnically ruptureable composite structural component 1 shownby way of example in FIG. 1 secures elements 2 and 3 of a mechanicalstructure (not otherwise depicted) between which it is located. For thispurpose, the structural component 1, for example made of light alloy, isprovided at its ends with flanges 4 and 5 able to collaborate,respectively, with a flange 6 of the element 2 and with a flange 7 ofthe element 3 and clamping means 8 and 9 (depicted only by way of theiraxes in FIG. 1) securing the flanges 4 and 6 and the flanges 5 and 7,respectively.

The structural component 1 consists of a first part 10A, of a secondpart 10B and of means 10C of assembling said first and second parts.

The second part 10B bears the flange 5 and is therefore connected to theelement 3. At the opposite end to the flange 5, the second part 10B hasa free end 11, facing toward the first part 10A.

For its part, the first part 10A comprises two elements 12 and 13 fixedtogether by fixing means 14. At the opposite end to the element 13, theelement 12 bears the flange 4.

Facing the element 12, the element 13 has an open housing 15 in which adetonating pyrotechnic cord 16 is housed and which the element 12enters, closing off said housing 15. The fixing means 14 pass throughthe walls of the housing 15 (via holes 17) and the part of the element12 located therein, so as to secure the elements 12 and 13.

In the region of the housing 15, the element 13 has at least one region18 of preferential rupture.

At its free end 19, the opposite end to the housing 15 and to theelement 12, the element 13 has a widened head 20, for example with arectangular cross section.

The free ends 11 and 19 facing each other belonging to the parts 10B and10A are housed in a chamber 21 formed by said assembly means 10C. Thesemeans comprise two plates 22, 23 arranged on each side of the secondpart 10B and of the element 13 to delimit said chamber 21. At one end,the plates 22 and 23 are assembled rigidly with one another and with thesecond part 10B by clamping means 24 that pass all the way through them.At the other end, the plates 22 and 23 are assembled rigidly with oneanother by clamping means 25 which pass freely through the element 13via wide openings 26.

The free end 19 of the element 13 is enclosed by an open section 27,with an at least approximately omega-shaped cross section, made of avisco-elastic material such as a natural rubber, a silicone, anacrylonitrile butadiene or a polyurethane. The section 27 covers notonly the widened head 20 of the free end 19 but also the part 13A of theelement 13 adjacent to said widened head 20 and forming part of saidfree end 19. Thanks to the clamping means 24 and 25, the plates 22 and23 press said section 27 against the free end 11 of the part 10B, on theone hand, and against the part 13A and the widened head 20 of theelement 13, on the other hand.

Thus there are confined portions of the section 27 between the free endsof 11 and 19 and between said free end 19 and the plates 22 and 23.

It will therefore be readily understood that the stiffness of theassembly means 10C depends essentially on that of the material of whichthe section 27 is made and, in particular, on the compressibility ofthis material. It will in fact be noted that, whatever the direction andnature (compression, elongation, bending, torsion, etc.) of the forcesapplied to the assembly means 10C, these means cause part of the section27 to be compressed:

-   -   either between the free ends 11 and 19;    -   or between the widened head 20 and the plates 22 and 23;    -   or alternatively still, between the part 13A and the plates 22        and 23.

As mentioned hereinabove, in order at least roughly to tune thestiffness of the section 27 to the magnitude of the forces applies tothe assembly means 10C, the external surface thereof, which is incontact with the widened head 20, has cavities 28 allowing theconstituent material of said section 27 to expand.

When the element 2 has to be separated from the element 3, thepyrotechnic detonating cord 16 is initiated, so that the element 13 isbroken at the rupture regions 18, as illustrated schematically inFIG. 1. The detonation shock generated by activation of the pyrotechniccord 16 is propagated as far as the free end 19 of the element 13 but isprevented, if not completely at least in the main, from being propagatedto the part 10B by the section 27 which isolates the latter part fromsaid element.

1. A pyrotechnically ruptureable composite structural component intendedto transmit forces between a first and a second structural element andprovided with elongate pyrotechnic detonation separation meansincorporated in said structural component and able to break it so thatsaid first element can be separated from said second element along aline of separation, said structural component comprising: a first partin which said pyrotechnic separation means are incorporated and which isable to be connected to said first element; a second part able to beconnected to said second element; and means of rigid assembly of saidfirst and second parts via their free ends which are the opposite endsto said first and second elements respectively; said assembly meanscomprising damping means arranged between the free ends of said firstand second elements and able to damp the detonation shock propagating tothe free end of said first part when said pyrotechnic separation meansare detonated.
 2. The structural component as claimed in claim 1,wherein said assembly means form a chamber enclosing said free ends ofsaid first and second parts and confining said damping means betweensaid free ends.
 3. The structural component as claimed in claim 2,wherein said chamber is formed by lateral plates arranged on each sideof said free ends and secured only to said second part.
 4. Thestructural component as claimed in claim 3, wherein said damping meansextend laterally between said lateral plates and said free end of saidfirst part and are confined there.
 5. The structural component asclaimed in claim 1, wherein the free end of said first part comprises awidened head.
 6. The structural component as claimed in claim 5, whereinsaid damping means have a cross section in at least the approximateshape of a stylized omega, the internal cavity of which is filled bysaid widened head.
 7. The structural component as claimed in claim 1,wherein said damping means are in the form of an open section placedover the free end of said first part to enclose it.
 8. The structuralcomponent as claimed in claim 1, wherein the surface of said dampingmeans in contact with the free end of said first part comprises cavitiesallowing the constituent material of said damping means to expand whensaid assembly are subjected to mechanical stresses.
 9. The structuralcomponent as claimed in claim 1, wherein said damping means are of viscoelastic type.
 10. The structural component as claimed in claim 9,wherein said damping means are made of a material chosen from materialsin the group comprising natural rubbers, silicones, acrylonitrilebutadienes or polyurethanes.